Synapses are specialized structures that allow for the chemical and electrical communication of neurons with themselves, or with other cells, like for example muscle cells. During development, a failure to adequately form, maintain or transform synapses often leads to motor and behavioral deficits, learning disabilities, and mental retardation. Moreover, in the adult central nervous system the failure of axons to reestablish synaptic contacts prevents the recovery of function after injury. The formation and transformation of synapses requires the production of new proteins by the pre- and post-synaptic cells. Strong evidence indicates that some of these proteins are produced in the immediate vicinity of the synapse by the translation of selectively targeted mRNAs. Due to the difficulties to isolate pure axonal populations the identity of this subpopulation of mRNA remains elusive. The proposed aims are designed to develop in vitro tools to isolate and characterize mRNAs selectively targeted to axons. First, we will develop tissue culture approaches to facilitate the isolation of axons from their cells bodies of origin. This is a critical step to ascertain the identity of axonal mRNAs. The isolation of mRNAs from these subcellular compartments under different physiological and experimental conditions will allow us to detect not only messages constitutively targeted to the synapse but also those that produced and delivered under conditions leading to synaptic plasticity. Second, we will use Genechip analysis to identify the mRNA species present in these subcellular fractions. Third, identified genes will be organized in a database such that we can start comparative, clustering, and statistical analysis aimed to unveil regions in the mRNA molecule responsible for its localization and translational regulation. A comprehensive knowledge of the mRNAs targeted to the synapse and the signals that dictate their translation will increase our understanding of the mechanisms involved in synaptic plasticity and, ultimately, may lead to the development of new therapies that can alleviate some of the symptoms produced by trauma or aging.